It is known from the prior art, in particular from the document FR-A-2940375, to compute an optimum positioning of a part with respect to another part with which it must be assembled as a function of the effective defects measured over a plurality of points belonging to each of said parts at the level of the assembly interface. This optimization method allows the assembly of said parts in compliance with the functional requirements, starting from “post facto” measurements carried out on the real parts and relating to points situated at the interface. Said method makes it possible to find an assembly solution, that is to say a relative positioning of the parts with respect to one another and an assembly range, including in cases where all or some of points measured at the interface of one or the other part lies outside the manufacturing tolerances. The existence of such situations shows that in a good number of cases of assembly, in particular those which implement flexible large-size parts, the manufacturing tolerances imposed during the steps preceding assembly are not suitable:                said tolerances are too restricted, this giving rise to a manufacturing cost overhead with regard to the necessary actual need;        said tolerances are too wide, this giving rise to a cost overhead during assembly.        